A cortical modulating influence on hypoxically stimulated ventilation has been documented and a provisional localization has been identified in the orbital gyrus of the frontal lobe. Current experiments seek to determine whether an evoked response in this area follows carotid body stimulation. Other experiments with conscious, trained goats and cats have been designed to test phenomena of ventilatory control in the hypocapnic zone - a condition importantly dependent on cortical mechanisms. For those studies the hyperventilation of hyperthermia and hypoxia are under study, and for the latter, short and long term exposures are employed.